A wireless node location mechanism that employs a differential signal strength metric to reduce the errors caused by variations in wireless node transmit power, errors in signal strength detection, and/or direction-dependent path loss. As opposed to using the absolute signal strength or power of an RF...http://www.google.com.hk/patents/US20110183688?utm_source=gb-gplus-share專利 US20110183688 - Enhanced Wireless Node Location Using Differential Signal Strength Metric
